Jar



JAR

William K. Ansite, Glendale, Califl, assignor to Johnston Testers, Inc., Houston, Tex., a corporation of Texas Filed Oct. 10, 1956, Ser. No. 615,062

9 Claims. (Cl. 166-478) The present invention relates to jars, and, more specifically, to hydraulically operated jars.

In hydraulic jars employed heretofore, a mandrel is received in an annular housing and upper and lower seals are effected between the mandrel and the housing to define a fluid chamber therebetween. To keep the volume of the fluid chamber constant while the jar is extended and contracted, the cross-sectional area of the mandrel at each of the seals is made identical. Since the cross-sectional area of the mandrel at one of the seals must be relatively large to safely transmit the jarring blow, the effective area of the piston portion of the mandrel across which a pressure differential is created to retard extension of the jar has been relatively restricted. In consequence, a relatively high pressure build-up is experienced in the fluid chamber of such jars when they are tensioned, imposing severe requirements upon the seals.

It is, therefore, an object of this invention to provide a new and improved hydraulic jar in which the internal pressure build-up is minimized.

It is another object of this invention to provide a new and improved hydraulic jar with a one-way restricted flow valve having a low mass to prevent damage due to hammering.

It is a further object of this invention to provide a new and improved hydraulic jar of rugged construction and a relatively short length.

In accordance with the present invention, a jar is provided which includes an annular or tubular housing and a mandrel slidably received within the housing. The mandrel has large and small diameter sections, each section being sealed with respect to the housing to define a fluid chamber therebetween. The seal for the small diameter mandrel section is carried by an annular packing member slidable with respect to the housing and having a face. of restricted area exposed to pressure external to the housing. The mandrel carries an anvil for striking against a hammer portion of the housing. Between the anvil and the packing member is a piston carried by the mandrel having a passage therethrough which is restricted in one direction of piston travel by a low inertia valve. The piston travels Within a reduced diameter portion of the housing when the jar is initially extended and is subjected to a pressure difierential as the well string is tensioned. When the piston travels into a housing portion of larger diameter, the pressure differential is relieved and the anvil strikes swiftly against the hammer portion.

Other objects and advantages will become apparent in the course of the following detailed description.

In the accompanying drawing, forming a part of this application, and in which like numerals are used to designate like parts throughout the same,

Fig. l is an elevational sectional view of a jar embodying the invention.

Fig. 2 is a partial elevational sectional view of the device shown in Fig. 1 and on an enlarged scale, showing the parts in collapsed relation.

Fig. 3 is a view similar to Fig. 2, showing the parts in partially extended relation.

In the drawing, wherein, for purposes of illustration, is shown a preferred embodiment of the invention, reference numeral 10 indicates generally the jar tool, comprising an annular housing member 11 having a top hammer section 12, an intermediate section 13, and a lower section 14 connected together, the latter being adapted to be connected to a conventional grapple or other tool 16.

A tubular mandrel 17, comprising an upper section 18 and a lower section '19, is concentrically mounted in the housing member 11 for limited longitudinal movement therein. The upper mandrel section is connected to a top sub 21, which is, in turn, adapted to be connected to the lower end of a pipe string 22.

The housing section 13 is provided with adjacent portions 23 and 24 of different internal diameters, the portion 23 having an internal diameter greater than portion 24. The housing member and mandrel thus form a closed fluid chamber 26, with the mandrel extending completely through the chamber 26. The hammer portion 12 of the housing member is in sealing engagement with the upper mandrel section 18 and an 0-ring seal 27 prevents any fluid flow therebetween. The lower end of the chamber 26 is sealed by the floating annular packing member 28, adapted to move longitudinally with respect to the housing member 11 and mandrel 17. The portion of the mandrel section 19 which extends through the packing member 28 has a cross-sectional area considerably smaller than does the mandrel section 18. The floating packing member '28 carries an O-ring seal 20 in its bore which seals with the reduced section 19 of the mandrel. Since the cross-sectional area of the mandrel at the upper and lower seals 27, 20 is not the same, the volume of the chamber 26 tends to change with extension and contraction of the jar. To maintain the volume of the chamber constant, the packing member 23 has a lower portion of reduced external diameter defining a shoulder 25 directed away from the chamber and exposed to the pressure of well fluid communicated via lateral port 29 in the housing. O-ring seals 30 carried above and below the shoulder 25 by the packing member 28 engage the bore of housing section 14, which is stepped inwardly below the port 29 to define an annular chamber opposite the shoulder 25. By making the area of shoulder 25 substantially less than the area of the upper face of packing member 28, less than the full pressure of the well fluid may be exerted on the oil retained in the chamber 126 opposite the packing member. The external diameter of the reduced lower portion of the packing member 28 is identical to the external diameter of the mandrel section 18 to achieve a balance of well fluid pressures acting upon the mandrel, except for the excess pressure applied to shoulder 25.

The mandrel section 19 is radially enlarged to form a piston 31 adapted to fit snugly within the chamber portion 24 of smaller diameter, and rubber seal 32 is bonded to the external surface of the piston to prevent any fluid passage between the external surface of piston 31 and the internal surface of chamber portion 24. A plurality of longitudinal passages 33 is formed through the piston 31 to provide fluid communication from one side of the piston to the other side thereof. An annular valve member 34 is slidably mounted on the mandrel for movement towards and away from the piston passages 33. The valve member 34 is prevented from moving downwardly to completely cover the passages by a shoulder or valve seat 36 formed inwardly of the upper side of the piston 31. In the drawings, the clearance between the valve member 34 and the passages 33 outwardly of the shoulder 36 is exaggerated for purposes of illustra-- tion and the actual clearance is made so as to allow a relatively restricted flow through the passages when the valve member 34 is seated on shoulder 36. A resilient annular stop-member 37, preferably made of rubber, is disposed between the valve member 34 and the lower end of mandrel section 18, to urge the valve member 34 against the shoulder 36. Desirably, the effective upwardly facing area of the piston 31 is as large as possible to minimize pressure build-up.

The chamber portion 23 of larger diameter is provided with a plurality of splines 38 extending longitudinally of the housing section 13. The mandrel section 18 is radially enlarged at its lower end to form an anvil 39, and splines 40 are formed longitudinally of the anvil 39 to interiit with the splines 38 of the housing section 13. There are less anvil splines than housing splines and thus the fluid in chamber 26 may pass freely from one side of the anvil to the other side thereof through the grooves between the housing splines 38 unoccupied by anvil splines 40. The anvil splines 40 extend short of the upwardly facing impact face 41 of anvil 39.

The hammer section 12 of the housing member 11 is provided with a downwardly facing impact face 42 adapted to contact the impact face 41 of anvil 39 when the jar is extended fully.

Plugs 43 and 44 provide means whereby the fluid chamber 26 may be filled with a hydraulic fluid, such as oil.

In an exemplary use of the jar 10, the top sub 21 is connected to a well string 22 and the housing member 11 is connected to a grapple 16. The well string is lowered into a well and the stuck object (not shown) is clamped by the grapple in a conventional manner. With the mandrel 17 and housing member 11 in the collapsed position shown in Figs. 1 and 2, upward force is exerted on the well string. The fluid in the upper part of chamber 26 is put under pressure and is forced downwardly between the valvemember 34 and the upper face of piston 31 and through the piston passages 33. The rubber seal 32 prevents any fluid from passing by the outside circumference of piston 31. The piston moves slowly upwardly as the restricted flow through the passages 33 takes place. During this time, the upward force on the pipe string places a stretch on the pipe string.

When the piston 31 moves completely into the enlarged upper portion 23, the fluid in the upper portion of the chamber is free to by-pass the piston, as shown in Fig. 3, and the mandrel 17 moves upwardly in a sudden movement as the pipe string contracts. The impact faces 41 of the anvil 39 and 42 of the hammer sub strike together and produce an impact which is transmitted to the stuck object.

If this single impact is insufficient to dislodge the stuck object, the mandrel 17 is lowered downwardly in the housing member 11, moving the piston 31 back into the chamber section 24 of smaller diameter, again forcing the fluid to flow through the passages 33. However, the valve member 34 is forced upwardly by such fluid flow against the rubber stop member 37, which compresses to provide a greater clearance between the valve member 34 and passages 33, enabling the fluid to pass therebe'tween with'less restriction than on the upstroke of the piston 31. This enables the jar to be quickly reset to its normal collapsed position in readiness for another jar stroke.

As the jar is extended, the packing member 28 is forced upwardly by well pressure relative to the housing to maintain the volume of chamber 26 constant, although the mandrel moves upwardly with respect to the packing member. The pressure maintained in the lower portion of chamber 26 acting upwardly upon piston 31 is a fraction of the well pressure, dependent upon the area of the shoulder 25. By keeping this pressure small, the total pressure acting downwardly upon the piston 31 required to achieve a desired diflerential force on the mandrel may be minimized. For example, a pull of 40,000 pounds exerted on a previous type of jar having equal mandrel cross-sections at the upper and lower seals might produce a pressure build-up of 23,000 p.s.i. where the jar of the present invention of similar size has a pressure build-up of 13,500 p.s.i. at a like depth.

As may be appreciated, the jar may also be used with substantially the same operation when connected into the pipe string in its inverted position.

Because the anvil splines 40 terminate short of the anvil impact face 41, the anvil splines 40 do not strike the housing member hammer sub 12 and thus there is no force exerted on the anvil splines 40 which would cause them to shear off the anvil.

Due to the low mass of valve member 34- and the bias imposed on the valve member by the rubber stop member 37, damage from the hammering action of the valve member 34 on the anvil shoulder 36 is held to a minimum. No compensation for a decrease in viscosity of the hydraulic fluid due to temperature changes should be necessary, because the valve member 34 can easily be made to restrict the flow of fluid through the passages 33 to such an extent that the time difference in the retarding action due to a possible decrease in viscosity would be negligible.

It is to be understood that the form of the invention, herewith shown and described, is to be taken as a preferred example of the same, and that changes in size, shape and arrangement of parts may be resorted to, without departing from the spirit of the invention, or the scope of the attached claims.

I claim:

1. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation, said housing member and said mandrel being adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member having two adjacent portions of unequal diameter, a piston formed on said mandrel, said piston being in sealing engagement with the portion of said housing member of smaller diameter when said housing member and said mandrel are in collapsed relation and having a longitudinal passage providing fluid communication through said piston from one end of said chamber to the other end of said chamber, an annular valve member carried on said mandrel and slidable toward and away from said passage, means to urge said valve member towards said passage, means at one end of said piston for preventing said valve member from completely covering said passage whereby said valve member and said piston are adapted to allow a restricted fluid flow through said passage in one direction and to allow an unrestricted fluid flow through said passage in the other direction, an anvil formed on said mandrel, said anvil and said housing member having co-acting impact faces adapted to contact when said mandrel and said housing member move to extended position, said mandrel having different crosssectional areas opposite said upper and lower seal means, the seal means for the smaller area being slidable relative to said mandrel and housing member and having a face directed away from said chamber and exposed to pressure external to said housing member.

2. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation, said housing member and said mandrel being adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member and said. mandrel each having similarly disposed sections of unequal diameter, a piston formed on the mandrel section of smaller diameter, said piston being sealingly received in the housing section of smaller diameter when said jar is in collapsed relation and wholly received in the chamber section of greater diameter when said jar is in extended position, a longitudinal passage formed through said piston to provide fluid communication from one side of said piston to the other side thereof, an annular valve member carried on said mandrel and slidable toward and away from said passage, means to urge said valve member toward said passage, means at one end of said piston for preventing said valve member from completely covering said pasage, an anvil formed on said mandrel section of greater diameter, and a plurality of interengaging splines formed lengthwise of the housing and mandrel sections of greater diameter, the number of housing splines and mandrel splines being different to provide a fluid pasage, said anvil and said housing member having coacting impact faces adapted to contact when said mandrel and said housing member move to extended position.

3. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation, said housing member and said mandrel being adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member having two adjacent portions of unequal diameter, a piston formed on said mani drel, said piston being in sealing engagement with the portion of said housing member of smaller diameter when said housing member and said mandrel are in collapsed relation and having a longitudinal passage providing fluid communication through said piston from one end of said chamber to the other end of said chamber, valve means adapted to allow a restricted fluid flow through said passage in one direction and to allow an unrestricted fluid flow through said passage in the other direction, an anvil formed on said mandrel, said anvil and said housing member having co-acting impact faces adapted to contact when said mandrel and said housing member move to extended position, said mandrel having difierent cross-sectional areas opposite said upper and lower seal means, the seal means for the smaller area being slidable relative to said mandrel and housing member and having a face directed away from said chamber and exposed to pressure external to said housing member and a face exposed to pressure in said chamber, said firstmentioned face being smaller than said second-mentioned face.

4. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and extended relation, said housing member and said mandrel being. adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member having two adjacent portions of unequal diameter, a piston formed on said mandrel, said piston being in sealing engagement with the portion of said housing member of smaller diameter when said housing member and said mandrel are in collapsed relation and having a longitudinal passage providing fluid communication through said piston from one end of said chamber to the other end of said chamber,

valve means adapted to allow a restricted fluid'flow through said passage in one direction and to allow an unrestricted fluid flow through said passage in the other direction, an anvil formed on said mandrel, said anvil and said housing member having co-acting impact faces adapted to contact when said mandrel and said housing member move to extended position, said mandrel having different cross-sectional areas opposite said upper and lower seal means, the seal means for the smaller area being slidable relative to said mandrel and housing member and having a face directed away from said chamber and exposed to pressure external to said housing member and a face exposed to pressure in said chamber, said first-mentioned face being smaller than said second-mentioned face and means for effecting a seal between the outer surface of said piston and said housing portion, of smaller diameter.

5. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation, said housing member and said mandrel being adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing'member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member having two adjacent portions of unequal diameter, a piston formed on said mandrel, said piston being in sealing engagement with the portion of said housing member of smaller diameter when said housing member and said mandrel are in collapsed relation and having a longitudinal passage providing fluid communication through said piston from one end of said chamber to the other end of said chamber, valve means adapted to allow a restricted fluid flow through said passage in one direction and to allow anunrestricted fluid flow through said passage in the other direction, an anvil formed on said mandrel, said anvil and said housing member having co-acting impact faces adapted to contact when said mandrel and said housing member move to extend position, said mandrel having dilferent cross-sectional areas opposite said upper and lower seal means, the seal means for the smaller area being slidable relative to said mandrel and housing member and having a face directed away from said chamber and exposed to pressure external to said housing member and a face exposed to pressure in said chamber, said first-mentioned face being smaller than said secondmentioned face and wherein said slidable seal means has a portion of reduced external diameter substantially equal to the external diameter of said mandrel opposite the other seal means.

6. A well jar comprising an annular housing member and a tubular mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation, said housing member and said mandrel being adapted for connection in a pipe string above an object stuck in a well bore, upper and lower seal means for sealing between said housing member and said mandrel to form a closed fluid chamber with said mandrel extending completely through said closed chamber, said housing member and said mandrel each having similarly disposed sections of unequal diameter, a piston formed on the mandrel section of smaller diameter, said piston being sealingly received in the housing section of smaller diameter when said jar is in collapsed relation and wholly received in the chamber section of greater diameter when said jar is in extended position, a longitudinal passage formed through said piston to provide fluid communication from one side of said piston to the other side thereof, an annular valve member carried on said mandrel and slidable toward and away from said pass-age, means at one end of said piston for preventing said valve member from completely covering said passage, an anvil formed on said mandre l section of greater diameter, and a plurality of interengaging splines formed lengthwise of the housing and mandrel sections of greater diameter, the number of housing splines and mandrel splines being diiferent to provide a fluid passage, said anvil and said housing member having co-acting impact faces adapted to contact when said mandrel and said housing member move to extended position and an annular packer member carrying the seal means for the mandrel section of smaller diameter and slidable in said housing, said packing member having one face exposed to pressure in said chamber and an opposite face of lesser area exposed to pressure external to said housing member.

7. A well tool comprising an annular housing member and a mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other between a collapsed relation and an extended relation and adapted for eudwise connection in a well string, upper and lower seal means for defining a closed annular fluid chamber within said housing member and about said mandrel, a piston carried by said mandrel in sealing engagement with a portion of said housing member within said chamber and having a passage providing fluid communication lengthwise of said piston from one end of said chamber to the other end thereof, a valve seat on said piston and a valve member supported by said mandrel'for movement toward and away from said valve seat to control flow through said passage, said valve member and valve seat together affording a restricted continuation of said pas sage when said valve member and said valve seat are in engagement to permit retarded relative movement of said mandrel and said housing member, and said valve member and valve seat affording a relatively unrestricted con tinuation of said passage when said valve member is unseated from said valve seat to permit unretarded relative movement of said mandrel and housing member.

8. A well tool comprising an annular housing member and a mandrel concentrically mounted therein, said housing member and said mandrel being movable longitudinally relative to each other betwen a collapsed relation and an extended relation and adapted for endwise conmotion in a well string, upper and lower seal means for defining a closed annular fluid chamber within said housing member and about said mandrel, a piston carried by said mandrel in sealing engagement with a portion of said housing member within said chamber and having a longitudinal passage providing fluid. communication lengthwise of said piston from one end of said chamber to the other end thereof, an annular valve seat on said piston and a ring-like valve member slidably supported by said mandrel for movement toward and away from said valve seat to control flow through said passage, means for urging said valve member toward said valve seat, said valve member and valve seat affording a restricted annular continuation of said passage when said valve seat and said valve member are in engagement at an angle to the longitudinal dimension of said passage to permit retarded relative movement of said mandrel and said housing member, and said valve member and valve seat attording a relatively unrestricted continuation of said passage when said valve member is unseated from said valve seat to permit unretarded relative movement of said mandrel and housing member in the opposite direction.

9. A Well tool comprising an annular housing member and a mandrel concentrically mounted therein, said housing member and said mandred being movable longitudinally relative to each other between a collapsed relation and an extended relation and adapted for endwise connection in a well string, upper and lower seal means for defining a closed annular fluid chamber within said housing member and about said mandrel, a piston carried by said mandrel in sealing engagement with a portion of said housing member within said chamber and having a passage providing fiuid communication lengthwise through said piston from one end of said chamber to the other end thereof, said passage terminating in an annular shoulder short of an annular valve seat at one end 0E said piston, an annular valve member slidably supported about said mandrel for movement into and away from engagement with said valve seat, said valve member be ing slightly spaced from said shoulder when in engagement with said valve seat to provide an annular restricted continuation of said passage to permit retarded relative movement of said mandrel and said housing member, and said valve member and valve seat atfording a relatively unrestricted continuation of said passage when said valve member is unseated from said valve seat to permit unretarded relative movement of said mandrel and housing member in the opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 

